Mass spectrometers are analytical instruments that measure the mass-to-charge ratio of ions to allow the composition of a sample to be determined. They comprise three basic parts: an ion source; a mass separator; and one or more detectors. The ion source converts a gaseous sample into ions. The mass separator separates out ions of differing mass-to-charge ratio such that different ion species are incident on different detectors, or different parts of the same spatially sensitive detector. Commonly, the sample is ionised by electron bombardment, influence of a large electric field, or thermal ionisation, etc. A number of techniques are also known for performing the mass separation. For example, ions having different mass-to-charge ratios will be deflected by combinations of electric and magnetic fields by differing amounts. Hence, application of electric and magnetic fields across the path of the ions may be used to separate them into different species.
The majority of mass spectrometers are heavy items that take up a large amount of space.
Efforts have been made to reduce the size of mass spectrometers to enable them to be portable. For example, GB 2026231 describes such a device. Nevertheless, such devices continue to be large and expensive.
GB 2384908 and GB 2411046 describe miniature mass spectrometers. These devices require precision fabrication. The latter device also requires fine control of the flow of the gas sample. This is achieved by the use of a membrane.
All of the prior art devices are expensive. Some offer longer periods of operation and greater accuracy than others.
In medical diagnosis, it would be desirable to have accurate single use devices for testing of patients. After use the device would be disposed of, thereby avoiding passing on infection to other patients. Such a device would ideally be small and compact and the result could be easily and quickly obtained, perhaps by a nurse or patient's general practitioner or physician.